On Ubuntu 12.04 we simply installed the GStreamer-0.1 “gstreamer0.10-ffmpeg” plugin and mp4 files played fine with GStreamer’s “gst-play” tool.

But with Ubuntu 14.04 ffmpeg has been replaced with libav so that the ffmpeg plugin is no longer available as standard Ubuntu package. What is more, the libav plugin is only available for GStreamer-1.0 and not GStreamer-0.1.

For GStreamer-1.0 the missing libav codecs can be installed from the “ubuntu-restricted-extras” package:

sudo apt-get install ubuntu-restricted-extras

After that installation, “gst-play” will work again on Ubuntu 14.04. However, some other video players and internet browsers like Firefox explicitly require the ffmpeg plugin to be available, so we are basically out of luck for those applications on Ubuntu 14.04 and above. But, fortunately, it is possible to install the missing plugin from a PPA (yay ;-):

The QMediaPlayer class of Qt also relies on GStreamer to play videos. GStreamer-1.0 is not yet supported (at least not for Qt 5.7.0 and below), so the QMediaPlayer also requires the GStreamer-0.1 ffmpeg plugin to play MP4 files.

As a result, we need to install the following packages to enable the Qt media player with MP4 playback: